Once Again, Hubble Surprises Astronauts
Difficult Repair Proves Easy Task
Sunday, May 17, 2009
High above Earth, where the space shuttle Atlantis has lassoed the Hubble Space Telescope, some of the simple repairs have been heart-poundingly difficult, and many of the most daunting tasks have turned out to be a breeze.
So it went yesterday, with two astronauts ripping open an instrument and fiddling with sharp objects that posed a potentially lethal hazard to pressure-suited spacewalkers. Heralded as the most challenging spacewalk of the mission, it went like a dream -- and for at least one day, the aging Hubble and its eccentricities didn't give the astronauts fits.
John Grunsfeld, an astronaut-astronomer who has observed the universe via the Hubble and is also its most experienced repairman, joined crewmate Andrew Feustel in a six-hour, 36-minute repair job unlike anything attempted in orbit. The standard procedure for the Hubble is to swap old instruments for new ones in the most modular fashion possible, keeping it as simple as trading ink cartridges in a printer.
But yesterday what unfolded was a gearhead's fantasy, with Grunsfeld and Feustel, operating in the payload bay garage, pulling out all manner of customized tools and contraptions to bust open and fix the shorted-out Advanced Camera for Surveys.
To get inside the enormous camera, Grunsfeld first had to attach a plate that, when tightened, cut away a grid that covered an underlying panel. Then, with that panel exposed, he used a hand-held pistol-grip power tool to unscrew 32 fasteners, each of which had to be captured in a tiny plexiglass compartment to prevent it from becoming a hazard.
Grunsfeld's task was made all the more difficult by the awkward position of the instrument. He was unable to face the screws head-on, and had to approach from a 45-degree angle. A strut partially blocked his vision. A fear among engineers was that he would have a hard time visually confirming that each fastener had been loosened. As Grunsfeld worked, he called out how many turns each fastener required to become free.
"Click. Eight turns on number two, click about seven. . . . Eight and a half on number three . . . Eight and a quarter on number four . . ."
Successful, Grunsfeld then used a different tool to squeeze and then yank out four dead electronic circuit cards. Each card presented sharp edges that might nick a pressurized glove and expose the astronaut to the vacuum of space.
The white-knuckle moment went quickly and with only one hitch. For several minutes, the fourth and last card became stuck in place. Grunsfeld, panting a bit at times but always calm, declared simply, "I think we'll get it." He retrieved a tool resembling needle-nose pliers and, with much shaking and wiggling and prying, freed the card and delicately stowed it in a bag.
The astronauts also removed a refrigerator-sized, mirror-packed instrument called COSTAR, which was installed in 1993 to correct Hubble's blurry vision. It is no longer needed, because new instruments have the same corrections built in. The astronauts used the vacant slot to install a new instrument called the Cosmic Origins Spectrograph, which will probe the deep structure of the universe and search for filaments of dark matter that may bind together the galaxies in a kind of invisible cosmic foam.
The mission has been a triumph for NASA, but it has also been a bumpy ride for the astronauts and their support team on the ground. The Hubble has been idiosyncratic. In space, the telescope isn't the same creature as the mock-up in the deep pool at the Johnson Space Center, where the astronauts had simulated their spacewalks.
"After seven years without having people around, Hubble has lost its accommodation to people. It's gone wild again," said David Leckrone, the Hubble senior project scientist, after the second, rather harrowing spacewalk on Friday.